package network;

import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class UdpEchoServer {

    private DatagramSocket socket=null;
    //指定服务器socket要绑定的端口
    private static final int PORT=9090;
    public UdpEchoServer(int port) throws SocketException {
        socket=new DatagramSocket(PORT);
    }

    public void start() throws IOException {
        System.out.println("服务器启动！");

        while(true)
        {
            DatagramPacket requestPacket=new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            //当完成receive之后，数据都是以二进制的形式存储在DatagramPacket中
            //因此我们需要先将这个二进制数据转成字符
            String request=new String(requestPacket.getData(),0,requestPacket.getLength());
            String response=process(request);

            DatagramPacket responsePacket=new DatagramPacket(response.getBytes(),response.getBytes().length,requestPacket.getSocketAddress());
            socket.send(responsePacket);
            System.out.printf("[%s:%d] req=%s, resp=%s\n",requestPacket.getAddress().toString(),responsePacket.getPort(),request,response);
        }
    }
    public String process(String request)
    {
        return request;
    }

    public static void main(String[] args) throws IOException {
        UdpEchoServer udpEchoServer=new UdpEchoServer(9090);
        udpEchoServer.start();
    }
}
